Relating to a preparation method and application of a novel nanocomposite material, the invention provides a preparation method of a mesoporous silica-restricted gold nanocluster-induced fluorescence enhanced nano-fluorescent device and application of the same in copper ion detection, and aims to solve the problems of high cost, complex process and long detection time in existing copper ion detection methods. The method includes: 1. taking chloroauric acid as the raw material, adopting reduced glutathione as the reducing agent and stabilizer, and utilizing thermal reduction means to synthesize a gold nanocluster solution A from the bottom up under a high temperature stirring condition, loading the solution A into a centrifugal tube for centrifugation, taking the precipitate, using a mixed solution of acetonitrile and water to perform washing 3 times and performing dissolving in deionized water to obtain a solution B; 2. making TEOS, ethanol, water and ammonia water into solid silica particles by Stober process, washing and drying the silica particles, then taking NaoH as the etchant, and performing sealed stirring overnight in a flask, then loading the obtained solution into a centrifugal tube for centrifugation 3 times to remove the precipitate left by the supernatant, and performing washing and drying to obtain mesoporous silica; and 3. putting the mesoporous silica into the solution B under a stirring condition so as to obtain the novel nanocomposite material with specific detection application in cooper ions. The composite material prepared by the method has the characteristics of low cost, simple operation, rapid detection and high sensitivity, and can be used in the fields of environmental ion detection and bioimaging.